A problem in treating chocolate masses may arise when also solid matter is to be kneaded in, for example nuts. The same problem may arise when the paste itself should have formed hard, cloddy particles by way of agglomeration. It has become apparent that the number of revolutions of the treating rotor, which, to a certain extent, also determines the treating performance of the device, will then be limited, particulary in such a case. At times, an accumulation of the solid matter or agglomerates to be kneaded in can then be observed on the trough wall, so that the homogeneity will no longer be completely assured. Hitherto, this manifestation has been tolerated, at the most one has taken the measure to reduce the number of revolutions of the treating rotor.